A doctor in the Top End town of Katherine is "very angry and upset" at both tiers of Government, after blood testing revealed some residents had "exceedingly high levels" of a potentially toxic chemical in their blood.

Key points:

Blood tests were offered to Katherine residents due to concern water supply could be contaminated

Levels of one chemical found at more than 40 times safe levels

Lack of research left it unclear if chemical poses risk to human health

International studies have shown the PFAS chemicals may be linked with cancers, ADHD and poor brain development.

'We have seen some exceedingly high levels'

Dr Spafford pointed out that the chemical recorded in such high levels in Katherine residents, one of the PFAS chemicals known as PFHxS, was on a European list of "substances of very high concern".

He said studies had shown the chemical would stay in humans for seven to eight years, much higher than the animals that affects of the chemicals were tested on.

"I think the Department of Health is still sticking to their story that … there is no consistent evidence to say that it causes health problems — but the problem is that it hasn't been well researched," Dr Spafford said.

"The studies that they've done on animals are not equatable to those that they've done on humans.

"The big problem and the big reason that it's on that substance of very high concern [list] is because of it's bioaccumulation potential in humans.

"In fact the half life is seven to eight years [in humans]. The half life in the rats is about 24 hours."

Lack of clarity remains

Dr Spafford was critical of the Department of Health's management of the testing, and said he was never warned the chemical may show up prior to carrying out the testing.

He also had not been able to view data from blood testing carried out in other regions where PFAS was used, such as Williamstown and Oakey, making it difficult to interpret what the high levels meant.

That meant when community members came to him asking if they should be concerned about their levels, he didn't know what to tell them.

"[Blood tests have shown] certainly very high levels that number 40 times the safe levels," Dr Spafford said.

"We have seen some exceedingly high levels. That's all I can really interpret at the moment."

However, he said two other chemicals from the PFAS group — PFOA and PFOS — were at acceptable levels in the majority of tested residents.

But one resident, who drank water from a bore, had a PFOS recording so high it was "unreadable, off the charts".

Funding for blood testing will continue until April next year, and residents are encouraged to access the service.

'I am angry about it'

Dr Spafford said the NT Government would have been aware of the risk of contamination to the water supply when the RAAF stopped using the firefighting foam in 2004.

Yet he said it had failed to monitor whether or not that had happened, putting the Katherine community at risk.

"The NT Government was actually irresponsible and absolutely culpable in my view of not monitoring it leaking into the water supply and contaminating its own population," he said.

"I am angry about it. I feel as if they had taken responsible steps at that time none of this would be a problem now."

Lack of mental health support

When asked whether the community had been provided with adequate mental health support, he said: "The answer would be no."

Although Dr Spafford said the community was promised additional mental health support workers, he said none had been appointed.

"Again it's this sort of, 'Oh, we'll get around to it'. And I find that concerning," he said.

"It's sort of this attitude of, 'Oh we'll do a few tests and that will keep them all happy'."

Health Minister Natasha Fyles said the NT Government had been "extremely concerned" about the legacy PFAS issues in Katherine.

"We have been working with the Federal Government, lobbying them, to make sure the Northern Territory is not forgotten and that we have the appropriate supports in place for those residents," she said.

Th Federal Government was contacted for comment but was yet to respond.